In U.S. Pat. No. 4,263,892, Frederick H. Little and David C. Little in 1981 described their heat sensing means, particularly used with solar water heating apparatus. They provide temperatures differential sensing means for sensing temperatures at the respective opposite sides of a heat shield in turn supporting a solar collector. By so doing they monitor the alignment of the heat shield and solar collector with respect to the sun to maintain the heat shield and solar collector in operative aligned relationship with the sun throughout each day. Their temperature sensing chambers are filled with air and connected to pressure sensitive pilot actuators, each actuator having a diaphragm commonly connected to the other diaphragm. The diaphragms move only in response to changes in temperature between the air filled sensing chambers, and not to variations in ambient temperatures. The common connection between the diaphragms is also connected at its midpoint to an actuating lever of a three way valve assembly. This valve assembly moves to admit or to drain water from a servo actuator, which moves the solar heat collector and its heat shield about an axis alternately in both east and west directions.
Some other patents which illustrate and describe the use of two pressurized temperature sensors, utilizing the expansion of fluids under pressure and temperature, which sensors are spaced apart in locations differently receiving the heat from the sun, when their associated solar collector is not closely tracking the sun, and whereby the differential of pressures created by these temperature sensors effectively acts through an associated actuator assembly to cause realignment of the solar collector with the moving sun, are:
U.S. Pat. No. 3,680,307 L. W. Michalec's Heat Energy Transfer Device;
U.S. Pat. No. 4,159,710 G. Prast's Solar Collector Comprising Solar Tracking Means;
U.S. Pat. No. 4,185,615 E. W. Bottum's Solar Collector Structure;
U.S. Pat. No. 4,198,954 R. J. Meijer's Solar Collector Comprising Solar Tracking Means;
U.S. Pat. No. 4,211,212 R. J. Braun's Solar Refrigeration System; and
U.S. Pat. No. 4,262,654 C. J. Ward's Solar Energy Powered Sun Tracker.
Some other patents which illustrate and describe the use of resilient and/or compactable and collapsible hoses or tubes, which is expanding to receive the pressurized volume of fluids, move related components, are:
U.S. Pat. No. 2,987,004 J. L. Murray's Fluid Pressure Device;
U.S. Pat. No. 3,014,459 J. A. Gustair's Reciprocating Motion Device;
U.S. Pat. No. 3,045,611 J. L. Murray's Fluid Pressure Devices;
U.S. Pat. No. 3,417,942 E. M. VanAlstyne's Projectable Structure;
U.S. Pat. No. 3,494,260 J. L. Critcher's Actuator; and
U.S. Pat. No. 3,673,924 S. Zakrezewski's Fluid Motors.